1. Field of the Invention
The invention relates to a method for decomposing organic compounds by a microorganism having an organic compound decomposing ability, a apparatus for decomposing organic compounds by a microorganism having an organic compound decomposing ability, a method for isolating a microorganism, and a new organic compounds-degradable microorganism.
2. Description of the Related Art
Leakage into the environment of organic compounds including halogenated hydrocarbon such as trichloroethylene, dichloroethylene, vinyl fluoride, vinyl bromide, 3,3,3-trifluoro-2-propene and 2,3-dichlorohexafluoro-2-butene, and aromatic hydrocarbon such as toluene, phenol, bromobenzen, 1-bromonaphthalene and cresol used as a cleaning agent in various types of plants has become a serious problem in these years. As to the use of organic compounds, studies are now being made toward the restriction of their use. But, the environments which have been contaminated by organic compounds, for example, contaminated soil and contaminated underground water, are problems remained to be solved.
Under such circumstances, studies are being made on the cleaning of the environments such as soil and underground water contaminated by organic compounds. For example, proposals have been made to clean the contaminated environments by physical methods such as soil vapor-extracting and incinerating. As a technique which is inexpensive and has a lower environmental impact as compared with the physical methods, a method for decomposing organic compounds contaminated the environments by a microorganism is attracting attention. And, as techniques for directly treating organic compounds, a thermal or optical decomposing method are known. But, a method for decomposing an organic compound by a microorganism is attracting attention because this method is superior to the above treating techniques in costs and operability.
As examples of a method for decomposing an organic compound by a microorganism, the proposed are a method of using methanotroph which needs the addition of methane (see Japanese Patent Laid-Open Publication No. Hei 2-92274), and a method of using bacteria which needs the induction by an aromatic compound such as phenol, toluene or cresol (see Japanese Patent Laid-Open Publication No. Hei 8-66182), and a method of using mutagenized bacteria (see Japanese Patent Laid-Open Publication No. Hei 8-228767).
However, such conventional methods for decomposing an organic compound by a microorganism have disadvantages that it is hard to keep the decomposition efficiency (treating efficiency) of the organic compound because they need additives, inducers and mutagenized bacteria, and in the case of applying such methods to the clean up of contaminated environments, additional contamination (secondary contamination) may be caused because new substances including additives and inducers are added to the environment, resulting in not cleaning up the environment. Especially, the latter method is highly possible to additionally contaminating the environment because it uses a microorganism which needs the induction of the enzyme by an aromatic compound such as phenol, toluene or cresol which is hazardous to the environment. Furthermore, when mutagenized bacteria are scattered to the environment, it is a great menace to the safety in society.
In other words, the conventional methods for decomposing an organic compound by a microorganism have disadvantages that inducing substances must be added to the environment to induce enzymes necessary for decomposition, or mutagenized bacteria must be scattered to the environment for decomposition, and when inducers such as hazardous chemicals are necessary, or mutagenized bacteria are scattered to the environment, it is highly possible to cause secondary contamination if such conventional methods are applied to the cleanup of the contaminated environment, so that it is hard to clean the environment contaminated by an organic compound. And, the methods for decomposing an organic compound by a microorganism also have a disadvantage that it is hard to keep the decomposing operation and the decomposition efficiency because the additives and inducers are required.
Therefore, it is highly demanded to provide a method for decomposing an organic compound by which, for example, an organic compound in the contaminated environment can be decomposed effectively without adding any new substance such as an additive and inducer or mutagenized bacteria, to environment, and the decomposing operation and the decomposition efficiency of the organic compound can be kept easily; microorganisms which can effectively decompose organic compounds without requiring a new substance such as an additive or inducer; and a microorganism isolating method which can readily isolate the above microorganism.